Genetics: Modes of Inheritance

Question 1

Autosomal Dominant Disease Homozygotes

Answer 1

Usually lethal

Question 2

Achondroplasia

Answer 2

Dwarfism from AD FGFR3 mut

Question 3

Hemizygous

Answer 3

Males are for all genes on X chromosome

Question 4

Allelic Heterogeneity

Answer 4

Different mutations in same gene may cause the same disease

Question 5

Compound Heterozygosity

Answer 5

2 different abnormal alleles at the same locus in an individual

Question 6

Locus Heterogeneity

Answer 6

Different muts in different chromosomes causing the same disease

Question 7

Sex Limitation

Answer 7

Autosomal dominant disorder expressed exclusively in males

Question 8

Mosaicisim

Answer 8

Ocurrence of 2+ cell lines with different genetic or chromosomal constitutions

Question 9

2 Kinds of Mosaicism

Answer 9

Germline - some of germ cells are, mutation transferred to offspring as affected, not mosaic
Somatic - milder/segmental phenotype, cannot be passed to offspring unless present in germline

Question 10

Classic Pedigree of Mt Inheritance of Disease

Answer 10

Woman affected, all her children are affected, none of the children of her sons are affected

Question 11

4 Differences b/w Nuclear and Mt Genome

Answer 11

Mt WAY smaller/fewer genes
Mt ring-shaped
Mt way higher percentage of coding DNA
Mt no introns

Question 12

Heteroplasmy

Answer 12

An mtDNA variant is found only in a portion of cell’s mt

Question 13

Homoplasmy

Answer 13

All mtDNA copies have same sequence/mut

Question 14

3 Mitochondrial DNA Point Mutation Diseases

Answer 14

tRNA gene: Mitochondrial encephalomyopathy (MELAS)
ATPase gene: Neuropathy, ataxia, and retinitis pigmentosa (NARP)
ETC Complex 1: Leber’s hereditary optic neuropathy (LHON)

Question 15

3 Mitochondrial DNA Large Deletions Diseases

Answer 15

Chronic progressive external ophthalmoplegia (CPEO)
Kearns-Sayre (triad of CPEO, bilateral pigmentary retinopathy, and cardiac conduction abnormalities)
Pearson Syndrome (a lot of shit)

Question 16

Disease Concordance b/w Monozygotic and Dizygotic Twins by Genetic or Multifactorial Cause

Answer 16

Genetic: MZ 100%, DZ up to 50%
Multifactorial: MZ <100%, DZ less than MZ

Question 17

Heritability

Answer 17

Proportion of total phenotypic variance of a condition which is caused by genetic variance

Question 18

Threshold Theory of Qualitative Traits

Answer 18

Susceptibility (liability) depends on the combined small effects of many genes and shows a bell-shaped distribution in the population, and only proportion of individuals exceeding a certain threshold develop the disease

Question 19

Qualitative vs. Quantitative Trait

Answer 19

Qualitative is dichotomous, quantitative continuous

Question 20

5 Factors Contributing to Higher Liability

Answer 20

Number of affected relatives
Severity of phenotype
Individual is affected w/ disease that has low incidence in general pop
Proportion of genes in common w/ affected family relatives (closeness of relation)
Affected individual belongs to less frequently affected gender